Fruitcake is often the butt of jokes, including one by comedian Johnny Carson that all fruitcakes were actually one single fruitcake re-gifted year after year. But you might be surprised to find out exactly how long the shelf life of fruit cake can be when it's stored properly. In 2011, a 70-year-old fruitcake originally bought at a grocery store sold for more than $500 at auction.

Fruitcakes date as far back as the ancient Romans, with the earliest known recipe including pomegranate seeds and pine nuts baked into barley mash. Throughout the centuries, recipes evolved to the modern form featuring spices, nuts, candied fruit, sweetener and alcohol. The two most common types of fruitcake are light, with granulated sugar, nuts, golden raisins, pineapple and apricots, and dark, made from molasses, brown sugar, raisins, dates, cherries, and pecans or walnuts. The key ingredient to maximum shelf life is the microbe-killing alcohol. One such fruitcake baked in 1878 and kept as a family heirloom was safely sampled by Jay Leno on "The Tonight Show" in 2003.

To make sure your fruitcake can be eaten months or years from now, take several towels and soak them in brandy, spiced rum, or your favorite alcohol. Then wrap the towels around the cake and let it soak for awhile, before soaking the actual cake in even more alcohol. Finally, wrap the fruitcake in clean towels, then either plastic wrap or aluminum foil, and periodically soak the cake in more alcohol over a period of months. To extend shelf life further, bury the liquor-soaked cake in powdered sugar and place it in a tightly covered container in a cool place.

Even a well-preserved fruitcake can go bad. You may notice it's hard and dry, especially if the alcohol-soaking process wasn't as thorough as it should have been. If you see any mold on if the cake, if it appears slimy or mushy, or if there is a rotten smell or sour taste, don't take any chances and throw the cake away. Eating fruitcake contaminated with bacteria can cause food poisoning. You should also know that rich, fatty foods like fruitcake can be dangerous to dogs susceptible to attacks of pancreatitis.

If you think you've eaten a contaminated fruitcake, see a doctor or seek emergency medical help. Untainted, fresh fruitcake is generally safe to eat during pregnancy if alcohol was only used in the cake batter, and the cake wasn't soaked in alcohol afterward. If you're pregnant, check with your doctor if it's OK for you to eat fruitcake.